During the drilling of oil and gas wells, unpredictable and unwanted borehole diameter enlargement may occur in addition to the primary borehole drilling. Specific intervals or locations of borehole diameter enlargement, or “out-of-gauge” portions, are undesirable discontinuities in the overall “in-gauge” character of a good borehole. Borehole enlargement can cause problems when tripping or pulling the drillstring out of the borehole, and when running casing. Sections of borehole enlargement can create “tight” hole conditions for the drillstring or casing, wherein the borehole is closed off to proper axial movement of the drillstring or casing, which result in operational time loss during a single trip of the drillstring or casing string. For example, borehole diameter enlargement can cause the loss of one to two days of expensive rig time due to the interruptions in tripping or running. Extended reach and/or high-angle wells are susceptible to localized borehole enlargement, and the problems created thereby are exacerbated in such wells.
Possible causes of hole enlargement include the mechanical and hydraulic damage from the bottomhole assembly (BHA) and mud across the BHA, insufficient mud weight, excessive pressure or hydraulic horsepower per square inch (HSI) drop on the drill bit, excessive flow rate and mud viscosity, drillstring vibration, and others.
It is difficult, in the field, to identify the cause of drillstring tripping or casing running problems, and in particular correlating these problems specifically with borehole enlargement. Further, after borehole enlargement is identified, it is difficult to determine the cause of the enlargement. The present disclosure overcomes these and other limitations of the prior art.